Ok, so my choo choo 1999 Suburban A/C is acting very strange.... I just replaced the compressor/drier/orifice tube and charged the system with 4 lbs. My low pressure at 1200 RPMS is 32 and 250 with outside temp 90. My center dash temp is 60 degrees. When I turn on the rear A/C the system pressures go to 70 and 250.... The rear uses an expansion valve so I assume it is stuck open, but when it is off, could it be bleeding into the front A/C keeping it from cooling? I am stumped on this one. Need my tow vehicle back! Anyone have experience on these systems? Thanks, Jon
Jon did you blow some air through the lines to the rear? I have seen some problems with too much oil in the lines and it has accumulated in the rear systemo No: why it just does. You could vac it down blow out the rear and try again. How much oil did you put in the new compressor? Check to see if there is a filter to the rear also , I don't know if there is...
The front uses an orifice tube, the rear A/C is controlled by an expansion valve. My question is if the expansion valave is stuck in the open position, would it cause the high pressures on the low side when engaged? Also, when the rear system is not on, is it possible that it is still allowing the system to pass freely on to the low side? Getting to the rear expansion valve is a 3 hour job, so I sure want to diagnose before I go through that. I guess I could blow air through the system as suggested and see if it is indeed closed if the expansion valve is in the closed position. My pressures seem right on for the front A/C yet it is only cooling to 60 degrees. What else could cause that? Thanks, Jon
Was the system working properly before it needed the compressor? What is the specified refrigerant charge for the system? How much oil did you add to the system? Did you replace the orifice with the same color tube? What was wrong with the old compressor? Before you open the refrigerant loop, if possible, test the rear TXV by dipping the sensing tube in hot and cold water with the system running. You should see the change in pressures if it's working. Judging from your pressures, it looks like it's working.
I changed the compressor because 70lbs on the low side is not the behavior of a good compressor. It generally indicates a bleed problem inside the compressor and since these HT6 compressors are known for being leaky, I replaced it with a Sanden redesigned model. The refrigerant capacity is 4lbs and that is what is in the system. When I opened the system up the oil looked very clean and there was no contamination on the orifice tube so I did not flush the system because it is a horrible complex system. I would have done more harm than good. I tool 6 oz out of the compressor and drier and the compressor came with 7 oz. I have a strong suspicion that the rear TRX valve is stuck open which is causing high pressures on the low side.
Sounds like you covered the bases. I was concerned that there may have been too much oil or some debris in the system. Good call, ditching the HT6, BTW. Those Sanden based replacements are real problem solvers. Do you have a way to measure the temperature of the tubes going into the front evaporator? I'm curious as to the actual evaporator temp.
